Digital pay TV programming delivered to cable and satellite set top boxes (STBs) long have been provided with conditional access and digital rights management (DRM). As conventionally understood, conditional access refers to the control of access to particular transmission or broadcast, regardless of the specific content in such transmission or broadcast. PowerKEY of Scientific Atlanta and MediaCipher of Motorola are common examples of conditional access technologies. Also, as conventionally understood, DRM refers to the control of access to a particular content, regardless of the mode of transmission or broadcasting of such content.
One conventional approach to cryptographic key management of current DRM systems involves the delivery of a normally-static content decryption key to each receiver, such as a cable or satellite STB, whereby the content decryption key is encrypted with that receiver's public key and digitally signed by the service provider, such as the cable-TV (CATV) or satellite-TV service provider. The receiver then uses the content decryption key to decrypt and access the content provided by the service provider. This conventional approach provides an inadequate level of security for premium content because the same static content decryption key is used for a single piece of content. Thus, whenever a service provider broadcasts that content, it can be viewed by anyone that possesses the content decryption key associated with such content, which key may have been compromised and illegally distributed over the Internet or the like. The scope of such security breach is potentially infinite and terminated only after it is discovered, and the content is re-encrypted with a new content decryption key.
Another problem associated with the conventional key management approach is that it does not scale well enough to support broadcast systems. This is because public key cryptography used to deliver a content decryption key to each user is too slow and would require an operator to invest in large amounts of expensive hardware. This is especially problematic for Pay-Per-View (PPV) broadcasts, where millions of potential users will request access within a relatively short period of time.